The quantum ground state of self-organized atomic crystals in optical resonators

Cold atoms, driven by a laser and simultaneously coupled to the quantum field of an optical resonator, can self-organize in periodic structures. These structures are supported by the optical lattice, which emerges from the laser light they scatter into the cavity mode, and form when the laser intensity exceeds a threshold value. We study theoretically the quantum ground state of these structures above the pump threshold of self-organization, by mapping the atomic dynamics of the self-organized crystal to a Bose-Hubbard model. We find that the quantum ground state of the self-organized structure can be the one of a Mott-insulator or a superfluid, depending on the pump strength of the driving laser. For very large pump strengths, where the intracavity intensity is maximum and one would expect a Mott-insulator state, we find intervals of parameters where the system is superfluid. These states could be realized in existing experimental setups.Comment: 11 pages, 4 figure

Entangling two distant oscillators with a quantum reservoir

The generation of entanglement between two oscillators that interact via a common reservoir is theoretically studied. The reservoir is modeled by a one-dimensional harmonic crystal initially in thermal equilibrium. Starting from a separable state, the oscillators can become entangled after a transient time, that is of the order of the thermalization time scale. This behavior is observed at finite temperature even when the oscillators are at a distance significantly larger than the crystal's interparticle spacing. The underlying physical mechanisms can be explained by the dynamical properties of the collective variables of the two oscillators which may decouple from or be squeezed by the reservoir. Our predictions can be tested with an ion chain in a linear Paul trap.Comment: 5 pages, 4 figure

Entangling two distant oscillators with a quantum reservoir

The generation of entanglement between two oscillators that interact via a common reservoir is theoretically studied. The reservoir is modeled by a one-dimensional harmonic crystal initially in thermal equilibrium. Starting from a separable state, the oscillators can become entangled after a transient time, that is of the order of the thermalization time scale. This behavior is observed at finite temperature even when the oscillators are at a distance significantly larger than the crystal's interparticle spacing. The underlying physical mechanisms can be explained by the dynamical properties of the collective variables of the two oscillators which may decouple from or be squeezed by the reservoir. Our predictions can be tested with an ion chain in a linear Paul trap.Comment: 5 pages, 4 figure

Full characterization of the quantum linear-zigzag transition in atomic chains

A string of repulsively interacting particles exhibits a phase transition to a zigzag structure, by reducing the transverse trap potential or the interparticle distance. The transition is driven by transverse, short wavelength vibrational modes. Based on the emergent symmetry Z_2 it has been argued that this instability is a quantum phase transition, which can be mapped to an Ising model in transverse field. We perform an extensive Density Matrix Renormalization Group analysis of the behaviour at criticality and evaluate the critical exponents and the central charge with high precision. We thus provide strong numerical evidence confirming that the quantum linear-zigzag transition belongs to the critical Ising model universality class. These results show that structural instabilities of one-dimensional interacting atomic arrays can simulate quantum critical phenomena typical of ferromagnetic systems.Comment: 5 pages, 4 figure

Spontaneous nucleation of structural defects in inhomogeneous ion chains

Structural defects in ion crystals can be formed during a linear quench of the transverse trapping frequency across the mechanical instability from a linear chain to the zigzag structure. The density of defects after the sweep can be conveniently described by the Kibble-Zurek mechanism. In particular, the number of kinks in the zigzag ordering can be derived from a time-dependent Ginzburg-Landau equation for the order parameter, here the zigzag transverse size, under the assumption that the ions are continuously laser cooled. In a linear Paul trap the transition becomes inhomogeneous, being the charge density larger in the center and more rarefied at the edges. During the linear quench the mechanical instability is first crossed in the center of the chain, and a front, at which the mechanical instability is crossed during the quench, is identified which propagates along the chain from the center to the edges. If the velocity of this front is smaller than the sound velocity, the dynamics becomes adiabatic even in the thermodynamic limit and no defect is produced. Otherwise, the nucleation of kinks is reduced with respect to the case in which the charges are homogeneously distributed, leading to a new scaling of the density of kinks with the quenching rate. The analytical predictions are verified numerically by integrating the Langevin equations of motion of the ions, in presence of a time-dependent transverse confinement. We argue that the non-equilibrium dynamics of an ion chain in a Paul trap constitutes an ideal scenario to test the inhomogeneous extension of the Kibble-Zurek mechanism, which lacks experimental evidence to date.Comment: 19 pages, 5 figure

Herpes simplex virus-type1 (HSV-1) impairs DNA repair in cortical neurons

Several findings suggest that Herpes simplex virus-1 (HSV-1) infection plays a role in the neurodegenerative processes that characterize Alzheimer's disease (AD), but the underlying mechanisms have yet to be fully elucidated. Here we show that HSV-1 productive infection in cortical neurons causes the accumulation of DNA lesions that include both single (SSBs) and double strand breaks (DSBs), which are reported to be implicated in the neuronal loss observed in neurodegenerative diseases. We demonstrate that HSV-1 downregulates the expression level of Ku80, one of the main components of non-homologous end joining (NHEJ), a major pathway for the repair of DSBs. We also provide data suggesting that HSV-1 drives Ku80 for proteasomal degradation and impairs NHEJ activity, leading to DSB accumulation. Since HSV-1 usually causes life-long recurrent infections, it is possible to speculate that cumulating damages, including those occurring on DNA, may contribute to virus induced neurotoxicity and neurodegeneration, further suggesting HSV-1 as a risk factor for neurodegenerative conditions

Satellite remote sensing for surface soil water content estimation

2008 - 2009Satellite remote sensing is a useful source of observations of land surface hydrologic variables and processes and could be a practical substitution of conventional in-situ monitoring. Most of hydrological dynamic processes change not only throughout the years but also within weeks or months and their monitoring requires frequent observations. The most prominent advantage of the remote sensing technologies is that they offer a synoptic view of the dynamics and spatial distribution of phenomena and parameters, often difficult to monitor with traditional ground survey, with a frequent temporal coverage. Many of the variables in the land surface water balance can now be observed with satellite techniques thanks to an extensive development over the last decades. Often the problem connected to the use of remotely sensed data is their accuracy that, according to the sensor used and to the application considered, can ranges from moderate to excellent. The objective of this thesis has been to evaluate the use of satellite remote sensing techniques for the monitoring of two variables useful for hydrology applications: water body extension and soil moisture monitoring. The capability to map water surface is important in many hydrological applications, in particular accurate information on the extent of water boundary is essential for flood monitoring and water reservoir management. Often, this information is difficult to retrieve using traditional survey techniques because water boundaries can be fast moving as in floods or may be inaccessible. In this PhD thesis, an artificial basin for which in-situ information about the water extension are available is used as case study. The area extension recorded daily by the dam owner is compared to the one retrieved by using satellite images acquired from SAR and TM/ETM+ sensors. The outcomes of the analysis show that satellite images are able to map water body surfaces with a good accuracy. The analysis also highlighted the factor to be taken into account while using types of sensors. Soil moisture is recognized as a key variable in different hydrological and ecological processes as it controls the exchange of water and heat energy between land surface and the atmosphere. Despite the high spatial variability of this parameter it has been demonstrated that many satellite sensors are able to retrieve soil moisture information of the surface layer at catchment scale. Among other sensors, the Scatterometer is very useful for climatic studies and modelling analysis thanks, respectively, to the temporal frequency, global coverage and to the long time series availability. Even though the ERS Scatterometer has been designed to measure the wind over the ocean surface, in recent years it has been pointed out that backscattering measurements have high potentiality for soil moisture retrieval. The second task of this PhD thesis, concerning the use of satellite data for soil moisture monitoring, has been developed at Serco S.p.A. in the framework of the Advanced Scatterometer Processing System (ASPS) project developed by ESA (European Space Agency) to reprocess the entire ERS Scatterometer mission. Since the beginning of the ERS-1 Scatterometer mission in 1991 a long dataset of C-band backscattering signal from the Earth surface is available for studies and researches. This is a very consistent dataset, but in particular for climatology studies it is important to have high quality and homogeneous long term observation as also stated in the key guidelines included in the Global Climate Observing System (GCOS) from the World Meteorological Organization (WMO). The main goal of this task has been the generation of the new Scatterometer ASPS products with improved data quality and spatial resolution. This achievement required a long preparation activity but represents an important contribution to the C-band Scatterometer dataset available to the scientific community. In order to evaluate the usage of the re-processed Scatterometer data for soil moisture estimation, the backscattering measurements derived in the new ASPS products have been then compared to in-situ volumetric soil moisture data and the relationship between radar backscattering and soil moisture measurements has been investigated under different conditions: angle of incidence, angle of azimuth, data measurements resolution, season of the year. Analysis results show that a relationship between the C-band backscattering coefficient and the in-situ volumetric soil moisture exists and takes into account the incidence and azimuth angles and the vegetation cover. [edited by author]VIII n. s

Quantifying the risk to life posed by hyperconcetrated flows

2012-2013In recent years, the disasters caused by landslides tragically increased due to the demographic growth and the indiscriminate use of land. Among the different types of landslides, flow-like phenomena - often simultaneously affecting large areas - are associated with the most catastrophic consequences in terms of loss of human life and economic damage. Understanding, forecasting and controlling the risk posed by flow-like phenomena are now recognised to be a priority for the safety of human life. As a result, a growing interest of both technical and scientific Communities, in performing risk analyses aimed at estimating the risk in a quantitative way has been recorded (Corominas et al., 2013). This PhD Thesis focus on the use of the quantitative risk analysis (QRA) procedures, specifically aimed at estimating the risk to life posed by flow-like phenomena. The use of QRA can allow the overcoming of some limits inherent to qualitative risk analyses in addressing practical problems (i.e. the prioritisation of management and mitigation actions as well as the allocation of associated resources). However, mainly theoretical contributions are provided on the topic at the international level. This can be due to the complexity of the procedures to be adopted for QRA purposes as well as to the significant amount of required input data (of both technical and socio-economic nature). The main goal of this research is to fill this gap by applying, improving and optimising the use of the QRA as a formal and structured tool for professionals involved in the management of the risk posed by flow-like phenomena. In this regard, the research activities focus on the quantitative estimation of the risk for loss of life, at medium and site-specific scale, posed by the occurrence of hyperconcentrated flows. The Thesis preliminarily provides a description of the main features of the flow-like phenomena, with an emphasis to those dealing with debris flows and hyperconcentrated flows. Then, the basic concepts and methodological approaches (with their limits and potentialities) of both qualitative and quantitative risk analysis and zoning are discussed. An overview of the current risk zoning in Italy, performed via qualitative risk analyses, is thus presented. On the basis of the above premises, the relevant benefits that, at regional and at site-specific scales, can be achieved passing from a qualitative to a quantitative risk analysis are highlighted. At medium scale, the analysis of historical records of landslide events in the Campania region (southern Italy) allows the identification and the characterisation of the different flow-like phenomena that may occur. In particular, these latter are individuated within a homogeneous geological context where carbonate slopes are covered by pyroclastic soils systematically affected by rainfall-induced slope instabilities later propagating as – often catastrophic in terms of life and properties losses – debris flows or hyperconcentrated flows. The thorough studies and researches carried out as well as the original results achieved allow to make relevant considerations – from both technical and scientific points of view – concerning both their spatial and temporal distribution (in terms of frequency) and the initial and boundary conditions which influence their occurrence. At detailed scale, the research activity focus on the quantitative estimate of the risk to life loss with reference to residents at the toe of Monte Albino (located in the Municipality of Nocera Inferiore (SA), Campania region), posed by the occurrence hyperconcentrated flows. The novelty of the proposed procedure consists in conjugating the fundaments of the risk theory with the geotechnical approach, providing a deeper understanding of the mechanisms that leads to the different and complex stages of movement. To this aim, a thorough in-situ investigations (with the purpose of framing the geological and geomorphological characteristics and to identify the 'hillslope' proneness to different slope instabilities, to characterise the spatial distribution of soil pyroclastic covers and their litho-stratigraphic structure) and laboratory tests (in order to have a complete physical and mechanical characterisation of the involved soils) are carried out. This study represents the indispensable prerequisite for the correct engineering modelling of phenomena at detailed scale - from the triggering stage to the propagation stage - obtaining in this way the definition of different hazard scenarios. The obtained results are used to estimate the expected consequences in terms of loss of human life with reference both to the most exposed persons within each of the impacted houses (to which corresponds the highest temporal-spatial probability) and to the average exposed person in open space (representing the average behaviour of a group of people). Finally, the procedure of quantitative risk estimate has allow to rank the portions of the urbanised territory at risk and, consequently, to provide a prioritisation of the areas needing structural mitigation measures. [edited by author]XII n.s

A novel method to titrate Herpes simplex virus-1 (HSV-1) using laser-based scanning of near-infrared fluorophores conjugated antibodies

Among several strategies used for Herpes simplex virus (HSV) detection in biological specimens, standard plaque assay (SPA) remains the most reliable method to evaluate virus infectivity and quantify viral replication. However, it is a manual procedure, thereby affected by operator subjectivity, and it may be particularly laborious for multiple sample analysis. Here we describe an innovative method to perform the titration of HSV type 1 (HSV-1) in different samples, using the “In-Cell WesternTM” Assay (ICW) from LI-COR, a quantitative immunofluorescence assay that exploits laser-based scanning of near infrared (NIR). In particular, we employed NIR-immunodetection of viral proteins to monitor foci of HSV-1 infection in cell monolayers, and exploited an automated detection of their fluorescence intensity to evaluate virus titre. This innovative method produced similar and superimposable values compared to SPA, but it is faster and can be performed in 96 well plate, thus allowing to easily and quickly analyze and quantify many samples in parallel. These features make our method particularly suitable for the screening and characterization of antiviral compounds, as we demonstrated by testing acyclovir (ACV), the main anti-HSV-1 drug. Moreover, we developed a new data analysis system that allowed to overcome potential bias due to unspecific florescence signals, thus improving data reproducibility. Overall, our method may represents a useful tool for both clinical and research purposes

thickness of pyroclastic cover beds the case study of mount albino campania region southern italy

ABSTRACTThe paper presents a method for estimating and mapping – at detailed scale (1:5000) – the thickness of pyroclastic cover beds resting on calcareous bedrock. This method, tested in the study area of Mount Albino (Campania region, southern Italy), makes use mainly of information gathered from in situ investigations, managed and processed in a geographical information system environment via a geostatistical interpolation technique (i.e. ordinary kriging) and finally integrated and amended by adopting a heuristic approach. Given its easy applicability and affordable costs, the proposed method can be used in similar geological contexts where knowledge of the spatial distribution of pyroclastic cover beds is a requirement for understanding and predicting slope instability processes